Effect of Silicon and Graphite Degeneration on High-Temperature Oxidation of Ductile Cast Irons in Open Air

Oxidation of Metals - The use of high silicon ductile irons is increasing as they offer some advantages with respect to conventional pearlitic–ferritic grades such as high elongation at...     

Experimental Design Applied for Cost and Efficiency of Antioxidants in Biodiesel

Oxidation stability is a parameter of great importance for biodiesel quality control to both producers and subsequent consumers. To maintain the quality of biodiesel, currently the most effective and economical method is the addition of antioxidants that prevent or retard the biofuel oxidation reaction. In this study, efficiency and cost of synthetic antioxidants added to B100 biodiesel from soybean oil and pork fat were evaluated, using butylhydroxyanisole (BHA), butylhydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ), in pure form or in mixtures, according to a simplex-centroid mixture experimental design. Results demonstrate an increased induction period (IP) in all trials when compared to the control sample, and TBHQ was the only antioxidant alone that met all the specification standards, while BHT and BHA alone met only the American standard specifications. The antioxidant mixture that presented the highest synergistic effect was that of TBHQ and BHA. Multi-response optimization indicated an optimum formulation containing 75 % TBHQ and 25 % BHA with an IP of 7.27 h at 110 °C and the antioxidant mixture cost of 31.31 USD, to be added for a ton of biodiesel. This simplex-centroid mixture experimental design shows an ability to be applied in the biodiesel, oils and fats industry to evaluate the oxidation stability and the occurrence of synergism between different mixtures of synthetic or natural antioxidants and their costs.     

A Fluorometric Enzymatic Assay for Quantification of Steryl Glucosides in Biodiesel

Steryl glucosides (SG) are common contaminants in biodiesel that form precipitates, which form and cause problems due to fouling during transport and storage. Therefore, their quantification is necessary to assess the quality of this fuel. The methods currently available for SG analysis require expensive instrumentation, need a previous concentration step by solid‐phase extraction (SPE) or are of limited use for the quantitative assessment. We developed an enzymatic method for SG quantification in biodiesel samples based on the hydrolysis of the glucoside catalyzed by a broadly specific beta glucosidase and the subsequent determination of the glucose released by the reaction. The method is non‐expensive, sensitive and was adapted to 96‐well format fluorescence plate reader, making it useful for the parallel assay of multiple samples. The enzymatic assay presented here represent a valuable tool for both quality control and the development of improved biodiesel production and purification procedures.     

The relationship between environmental management systems and organizational innovations

This study provides empirical evidence of the nature of the relationship between environmental management systems and organizational innovations. Using a sample of Spanish manufacturing firms, the study reports on the implementation of the International Organization for Standardization (ISO) 14000 environmental quality standards and the relationship of such implementation with organizational innovations in the firm. The study presents several implications of interest for practitioners, academics, and policy makers. © 2012 Wiley Periodicals, Inc.     

A new approach to spatial compression of stereoscopic videos

This paper presents a new spatial compression method specifically designed for stereo videos. Different form current compressors, which simply apply known 2D compression techniques, the method proposed here was developed taking into account specificities of the components of the spatial compression process which may impact the correct depth visualization, named Chrominance Subsampling, Discrete WaveletTransform (DWT) and Quantization. Each component was evaluated analyzing where datalosses occur and proposing ways to provide a good balance between compression ratio and image quality, minimizing losses in depth perception. The evaluations were made using standard objective (PSNR) and subjective (DSCQS) metrics, applied to an anaglyphic stereoscopic video base. The results showedour method is competitive regarding compression rate and providessuperior image quality.     

Global robust stabilization of nonlinear systems subject to input constraints

Our main purpose in this paper is to further address the global stabilization problem for affine systems by means of bounded feedback control functions, taking into account a large class of control value sets: p, r ‐weighted balls ??^m _r (p), with 1<p?∞, defined via p, r ‐weighted gauge functions. Observe that p=∞ is allowed, so that m‐dimensional r ‐hyperboxes ??^m _r (∞)?[?r₁^?,r₁⁺]×???×[?r_m^?,r_m⁺], r_j^±>0 are also considered. Working along the line of Artstein–Sontag's approach, we construct an explicit formula for a one‐parameterized family of continuous feedback controls taking values in ?? _r ^m(p) that globally asymptotically stabilize an affine system, provided an appropriate control Lyapunov function is known. The designed family of controls is suboptimal with respect to the robust stability margin for uncertain systems. The problem of achieving disturbance attenuation for persistent disturbances is also considered. Copyright © 2002 John Wiley & Sons, Ltd.     

Manufacturing of Mo-25 Re and Mo-50 Re Alloys by Means of Powder Sintering at Medium Temperatures

Powder mixtures of molybdenum and rhenium were sintered at various temperatures to fabricate Mo-25% Re and Mo-50% Re alloys. For this purpose, stoichiometric mixtures of the component powder metals with particle sizes of 1 to 5 μm average, were first homogenized in a planetary mill and then compacted at 300, 400, 500 and 600 MPa, to the shape of tablets and small billets for rolling to thin foils. The obtained pieces were subjected to sintering at various temperatures in the range of 1400 to 1700°C, under argon-hydrogen protecting atmosphere. The solid solution of rhenium in the molybdenum matrix was followed by means of x-ray diffraction. It was found that at all sintering temperatures rhenium was totally dissolved in theMo-25% Re alloy, while small amounts of an intermediate phase were detected in the case of the Mo-50% Re alloy, in good agreement with the corresponding phase diagram. The densification of sintered parts increased with temperature and compaction pressure up to values less than 90%. Owing to the fine particle size of the powders, the sintering temperature can be lower than those normally utilized in the refractory metals industry.     

Circadian rhythm of fatty acid desaturation in mouse liver

A study was made of the diurnal changes in liver microsomal desaturation of labeled stearic, linoleic and α-linolenic acids to oleic, γ-linolenic and octadeca-6,9,12,15-tetraenoic acids, respectively. C3H-S mice were used and were exposed to light-dark cycles. A circadian rhythm was observed for stearic acid desaturation, and a different one for linoleic acid. Linoleic and α-linolenic desaturation had similar responses in the day cycle. This would indicate that different mechanisms control the oxidative desaturations of the fatty acids in the 9 and 6 carbons. The fatty acid composition of the whole liver and liver microsomes also showed variations. Remarkable oscillations were observed for stearic and oleic acids. Neither the total protein synthesis nor the free fatty acid concentration in the microsomes followed a rhythm parallel to the desaturation of the studied fatty acids. The injection of cycloheximide 4 hr before measuring the desaturation modified the circadian variation of both the 9 and 6 desaturations. The modification induced by cycloheximide was considered to indicate that both variations are related to the synthesis of specific proteins but not to that of a degradative or inhibitory protein.     

Effects of emergent vegetation on lateral diffusion in wetlands

Constructed wetlands are widely used for a variety of environmental applications, such as wastewater treatment and recharge, and their efficacy is largely determined by the hydrodynamic characteristics of the flow system. An experimental study was carried out to quantify the lateral dispersion of passive substances in shallow zones of a constructed wetland wherein water flows though the interstices of the distributed vegetation. The experimental set up was designed to mimic the Tres Rios constructed wetland located in Phoenix, Arizona. The major emphasis was on the lateral diffusivity K(t) of a shallow zone with randomly distributed vegetation. The results are presented in the context of a simple theoretical model where K(t) is expressed in terms of the diameter of the plant stalk D(v), the characteristic distance between the plants d(v), the flow velocity U and the drag coefficient C(D) as (K(t)/UD(v))(d(v)/D(v))=betaC(D), where beta is a dimensionless constant. Fitting of data to the above model indicate that C(D), in general, is a function of the Reynolds number (Re). The data are also compared with a model proposed by Nepf et al. (Water Res 35 (1999) 479).